Wordpress security question

[Kamandor]

Okay, so i bought that book "Digging into wordpress"

And there it's says that prior the installation you should rename your "wordpress" folder to something weird and obscure.

Then you should go to index.php and

and change this

require('./wp-blog-header.php');
…to this:
require('./your_weird_and_obscure/wp-blog-header.php');

I did this and nothing works i get

Warning: require(.your_weird_and_obscure/wp-blog-header.php) [function.require]: failed to open stream: No such file or directory in /hermes/bosweb/web237/b2372/ipg.username/mydomain.com/your_weird_and_obscure/index.php on line 17

Fatal error: require() [function.require]: Failed opening required '.your_weird_and_obscure/wp-blog-header.php' (include_path='.:/usr/local/lib/php-5.2.17/lib/php') in /hermes/bosweb/web237/b2372/ipg.username/mydomain.com/your_weird_and_obscure/index.php on line 17

What do i do wrong?

And is there a way to do this thing if WP already installed and running? Is there a need to change something in database????